1. Field of the Invention
The present invention broadly relates to troubleshooting of aircraft cabin pressure control systems and, more particularly, is concerned with a tester which utilizes a pair of gages for determining the source or cause of a pressurization discrepancy in such control sytems.
2. Description of the Prior Art
It is conventional practice to pressurize an aircraft cabin to maintain a near sea level pressure therein. In a typical cabin pressure control system, such as found in Convair 340, 440 and 580 aircraft, air outside of the aircraft is routed to an air compressor which, in turn, forces it through air conditioning units to air ducts which deliver the pressurized air to the cabin. The air delivered to the cabin is constantly being relieved overboard by operation of a regulator valve. However, the regulator valve restricts the outflow of the cabin air to provide pressurization of the cabin. Control of the regulator valve by a pressure controller of the system establishes the pressure differential that is maintained during flight. Thus, the pressure controller permits selection of the pressure altitude at which the cabin will be maintained during flight. In the Convair aircraft, normal operation of the pressure controller causes the rate of airflow to vary from 73 pounds per minute at sea level to 65 pounds per minute at 20,000 feet, which is sufficient to change the air in the cabin approximately once every two minutes and provide a maximum pressure differential of 4.16 psi.
Heretofore, there was no satisfactory way to troubleshoot the pressurization control system without first removing the compressor and/or pressure controller from the aircraft to test them and without the aid of a specialized tester being available. Consequently, for quite some time, a need has existed for a convenient technique for troubleshooting the cabin pressure control system without having to first remove the suspected source of the problem to test it.